Federal and local law enforcement officers conducted 50 simultaneous raids in the pre-dawn hours Wednesday, taking down almost two dozen “high-ranking” suspected leaders of the notoriously violent MS-13 street gang, along with numerous Mexican Mafia leaders, in what is being described as the “largest gang raid in Los Angeles history.”

According to NBC News’ local Los Angeles affiliate, the raids were “the culmination of a three-year investigation,” in the words of the FBI’s Deidre Fike.

Led by the Los Angeles Metropolitan Task Force on Violent Gangs, the investigation began in June 2014, targeting the most violent actors and most senior leaders within the violent criminal enterprise controlled by MS-13, along with their ties to the Mexican Mafia.